block: clean up blkdev_get() wrappers and their users

After recent blkdev_get() modifications, open_by_devnum() and
open_bdev_exclusive() are simple wrappers around blkdev_get().
Replace them with blkdev_get_by_dev() and blkdev_get_by_path().

blkdev_get_by_dev() is identical to open_by_devnum().
blkdev_get_by_path() is slightly different in that it doesn't
automatically add %FMODE_EXCL to @mode.

All users are converted.  Most conversions are mechanical and don't
introduce any behavior difference.  There are several exceptions.

* btrfs now sets FMODE_EXCL in btrfs_device->mode, so there's no
  reason to OR it explicitly on blkdev_put().

* gfs2, nilfs2 and the generic mount_bdev() now set FMODE_EXCL in
  sb->s_mode.

* With the above changes, sb->s_mode now always should contain
  FMODE_EXCL.  WARN_ON_ONCE() added to kill_block_super() to detect
  errors.

The new blkdev_get_*() functions are with proper docbook comments.
While at it, add function description to blkdev_get() too.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Joern Engel <joern@lazybastard.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
Cc: reiserfs-devel@vger.kernel.org
Cc: xfs-masters@oss.sgi.com
Cc: Alexander Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 756a6798d7c8..0030640e2d72 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1147,14 +1147,14 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
 {
         struct nilfs_super_data sd;
         struct super_block *s;
-        fmode_t mode = FMODE_READ;
+        fmode_t mode = FMODE_READ | FMODE_EXCL;
         struct dentry *root_dentry;
         int err, s_new = false;
 
         if (!(flags & MS_RDONLY))
                 mode |= FMODE_WRITE;
 
-        sd.bdev = open_bdev_exclusive(dev_name, mode, fs_type);
+        sd.bdev = blkdev_get_by_path(dev_name, mode, fs_type);
         if (IS_ERR(sd.bdev))
                 return ERR_CAST(sd.bdev);
 
@@ -1233,7 +1233,7 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
         }
 
         if (!s_new)
-                blkdev_put(sd.bdev, mode | FMODE_EXCL);
+                blkdev_put(sd.bdev, mode);
 
         return root_dentry;
 
@@ -1242,7 +1242,7 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
 
  failed:
         if (!s_new)
-                blkdev_put(sd.bdev, mode | FMODE_EXCL);
+                blkdev_put(sd.bdev, mode);
         return ERR_PTR(err);
 }